Production of powerful oxidant, peroxynitrite (ONOO–) is considered as ‘reactive nitrogen species’ (RNS). Further this may further produce other reactive species similar to hydroxyl radical (•OH) however not always interaction between superoxide radical (•O2–) and nitric oxide (NO•) results in biologically harmful effect. During many enzymatic reaction, SOD-catalysed dismutation form O2 and hydrogen peroxide (H2O2) or it is formed by spontaneously reduction of two molecules of (•O2–). Hydrogen peroxide (H2O2) & superoxide radical (•O2–) enters into the cells in the same way as H2O enters. In the presence of transition metal ions like low molecular mass iron or copper,
There is also an ornithine transporter that transport ornithine from the cytosol into the matrix of the mitochondria. The rest of the reactions of the urea cycle occur in the cytosol. Second Step: The next step of the urea cycle is catalyzed by argininosuccinate synthetase. This enzyme uses ATP to activate citrulline by forming a citrully-AMP intermediate. In the second half of the argininosuccinate synthetase reaction, the α-amino group of aspartate attacks the imino carbon releasing AMP and producing argininosuccinate.
The four respiratory complexes are embedded in the inner membrane of the mitochondria, they are functionally very important to the electron transport chain and each of them have an individual role. (Tzagoloff, 1982) The first and the largest of these complexes is complex 1. Electrons are transferred to complex I, oxidizing NAD and reducing coenzyme Q. Electrons from succinate in the citric acid cycle are transferred to complex II and coenzyme Q. The electrons from coenzyme Q are then passed to complex III (cytochrome c) and IV (cytochrome c oxidase).
Chemical Reaction of Carboxylic Acids Main Contributor: Chen Swee Lun Carboxylic acids consists of a huge and diverse group of organic compounds that contain the carboxyl group (-COOH). The general formulae for carboxylic acid is CnH2n+1COOH. The presence of hydrogen atom in the carboxyl group gives carboxylic acids an acidic property when the acid is dissolved in water. Methanoic acid, ethanoic acid and propanoic acid are some examples of carboxylic acids. Formic acid, acetic acid and propionic acid are the common names for the three examples respectively.
• Serine, threonine and cysteine proteases use a nucleophilic residue (usually in a catalytic triad). That residue performs a nucleophilic attack to covalently link the protease to the substrate protein, releasing the first half of the product. This covalent acyl-enzyme intermediate is then hydrolysed by activated water to complete catalysis by releasing the second half of the product and regenerating the free enzyme. A comparison of the two hydrolytic mechanisms used for proteolysis. enzyme is shown in black, substrate protein in red and water in blue.The top panel shows 1-step hydrolysis where the enzyme uses an acid to polarise water which then hydrolyses the substrate.
In presence of sufficient molecular oxygen, NO reacts spontaneously to form N2O3, a reaction intermediate which can have deleterious effect on DNA by nitrosation of primary amines. It can also be noted that NO can react with superoxide (O2) to form peroxynitrate (ONOO-), an important Reactive Nitrogen Species (RNS) causing cellular and muatagenic effects. An introspection is needed in order to analyze the availability of nitric oxide and the rate of conversion into nitrites and
It can be converted to L-cysteine by its deacetylation, which can then be metabolised endogenously to produce H2S. Homocysteine can also be metabolised to form cysteine to produce H2S. H2S can also be produced via other mechanisms, such as the non-enzymatic reduction of elemental sulfur. Also, H2S can be released in alkaline conditions by sulfur stores found in cells. 2.3.1 Cystathionine-β-synthase (CBS) CBS is an enzyme that catalyses the first step of the trans-sulfuration pathway from homocysteine to cystathionine.
2.1 Chemistry of Bioluminescence Bioluminescence is the production of light as a result of a chemical reaction without the use of heat within a living organism. For bioluminescence to occur usually two substances and a by-product such as oxygen are required. In the majority of bioluminescent reactions, the chemical reaction which leads to bioluminescence is the oxidation of a molecule called luciferin. Luciferin, which is the substrate in this chemical reaction, is the chemical in the reaction which produces light. The reaction rate of this reaction is controlled by an enzyme called Luciferase which acts as a biological catalyst.
INTRODUCTION Carbon tetrachloride (CCl4) - an organic industrial solvent used in industry – is a vigorous carcinogenic agent that may create dysfunction of lung, liver, kidney and nervous system (1, 2). After being absorbed from gastrointestinal system, respiratory system and skin CCl4 is metabolized by cytochrome P-450 and exerts its toxic effects via its metabolites trichloromethyl free radical and trichloromethyl peroxyl radical (1-3). These free radicals interacts with fatty acids of lung cell membrane and increase lipid peroxidation and DNA fragmentation. Moreover, they suppress antioxidant enzymes including catalase, superoxide dismutase, glutathione (GSH), oxidized glutathione (GSSG), glutathione reductase and glutathione peroxide (1,2,4). CCl4 has been shown to cause lung toxicity by intra alveolar septa ruptures, interstitial cells degenerations and fibrosis owing to accumulation of
Firstly sulphide mineral is oxidised to form dissolved iron, sulphate and hydrogen, by the following chemical reaction. (Evangelou, V.P, 1998) 2FeS2+7O2+H2O→2Fe2+ +4SO4 2- +4H+ (Evangelou, V.P, 1998) (1) These dissolved chemical products represent an increase in solids and acidity of the water. Due to an exposure to oxidizing environment such as oxygen in the atmosphere, ferrous ions decompose further according to the following chemical reaction: (Evangelou, V.P, 1998) 4Fe2+ + O2+4H+→4Fe3+ +2H2O (Evangelou, V.P, 1998) (2) Fe3+ precipitates as Fe (OH) 3 thus further lowering